unit two

Question 1

what is the cryosphere?

Answer 1

parts of the earths crust and atmosphere below 0 degrees for at least a part of each year

Question 2

what does the cryosphere consist of?

Answer 2

ice sheets, glaciers, sea ice, lake ice, ground ice (permafrost) and snow cover

Question 3

what is topography?

Answer 3

the natural shape of the land that controls glacier morphology

Question 4

describe ice sheets and give an example of one

Answer 4

a gently sloping dome of ice several km thick in the centre. they are unconstrained and an example is the greenland ice sheet

Question 5

describe ice caps and give an example

Answer 5

a smaller version of an ice sheet which is a gently sloping dome over several km thick that submerges reigonal topography. they are unconstrained and an example is greenland

Question 6

describe an ice feild

Answer 6

ice covering an upland area that is not thick enough to bury the underlying topography, they are constrained

Question 7

describe a valley glacier

Answer 7

a glacier confined between valley walls. they tend to form ice caps/sheets and may be terminated in the sea. they are constrained

Question 8

describe piedmont glaciers

Answer 8

a valley glacier that extends beyond the end of a mountain valley into a flatter area. they are constrained

Question 9

describe a cirque glacier

Answer 9

a smaller glacier occupying on the hollow of a mountain side. they are constrained. an example is cwm idal

Question 10

describe an ice shelf

Answer 10

a large area of floating glacier ice extending from the coast where several glaciers have reached the sea. it is unconstrained

Question 11

describe cold based glaciers

Answer 11

glaciers found at high latitude locations where the ice temperature is well below zero. the glacier is permanently frozen to the bedrock, so there is no meltwater

Question 12

describe warm based/temperate glaciers

Answer 12

glaciers found in high altitude areas that have fluctuating temperatures. these glaciers are not frozen to the bedrock as there is meltwater present due to the pressure.

Question 13

what is pressure melting?

Answer 13

where ice melts from the pressure of the overlying glacial ice.

Question 14

what is the pressure melting point?

Answer 14

0 degrees

Question 15

why do temperate/warm based glaciers get meltwater at the bottom?

Answer 15

during summer months, when the temperature rises the top of the ice melts and this percolates down into cracks in the glacier leaving meltwater at the bottom

Question 16

what is regelation?

Answer 16

the melting and refreezing of ice due to changes in pressure

Question 17

when does basal sliding occur?

Answer 17

when there is meltwater at the base of the glacier which acts as a lubricant, allowing movement to occur

Question 18

what are the two basal sliding processes called?

Answer 18

• enhanced basal creep
• regelation slip

Question 19

describe enhanced basal creep

Answer 19

where ice comes into obstacles on the glacial bed but instead of melting, deforms as the pressure melting point has not been reached

Question 20

describe the process of regelation slip

Answer 20

when the temperature of ice is close to the pressure melting point then increased pressure on the upglacier side will induce melting. this allows glaciers to slip and flow around the obstacle so when it gets to the down glacier slide it can fall as the low pressure causes the down glacier side to freeze

Question 21

what is internal deformation?

Answer 21

the way cold based glaciers move as they cannot move by basal sliding. it involves the response of individual grains of ice within the glacier to the overlying pressure.

Question 22

what are the two types of internal deformation

Answer 22

Intergranual flow
Laminar flow

Question 23

describe intergranual flow

Answer 23

the displacement of ice grains relative to each other

Question 24

describe laminar flow

Answer 24

where layers of ice within the glacier slip over eachother

Question 25

what is ice creep?

Answer 25

the deformation of ice in response to stres. it is also a result of thicker ice or the surface slope angle

Question 26

what happens when a cold based glacier moves on a steep slope?

Answer 26

it is unable to move fast enough and so it fractures causing crevasses at the surface

Question 27

what is extensional flow?

Answer 27

when the slope gradient the ice is travelling along is increased and there is an acceleration of ice flow

Question 28

where does extensional flow often occur?

Answer 28

the zone of accumulation

Question 29

what is compressional flow?

Answer 29

when the slope gradient is reduced and the ice flow slows down allowing the ice behind to catch up and thicken, it usually closes crevasses

Question 30

what is subglacial bed deformation?

Answer 30

when a warm based glacier moves over weak rock causing the sediment to deform under the weight of the glacier, moving the ice on top of it

Question 31

how much movement does subglacial bed deformation account for in icelandic glaciers?

Answer 31

90%

Question 32

which have a greater velocity? warm based glaciers or cold based glaciers?

Answer 32

warm based glaciers

Question 33

how does slope angle impact on the rate of glacial movement?

Answer 33

if a glacier has a higher slope angle then it will move faster due to gravity

Question 34

how does the thermal regime of a glacier impact on glacial movement?

Answer 34

warm based glaciers have a higher velocity of ice movement than cold based glaciers due to pressure melting

Question 35

what are glacial surges?

Answer 35

periods of rapid movement where a glacier snout advances up to 1000 times faster normal

Question 36

what are glacial surges a result of?

Answer 36

a change in the flow pattern of subglacial meltwater

Question 37

what are the stages of a glacial surge?

Answer 37

1. pressure builds up underneath the glaciers in phases of normal glacier flow and there is an increase and thickening of ice in the accumulation zone 2, during winter, subglacial meltwater channels are closed increasing ice accumulation 3. during summer the weight of the ice accumulation is so great that the subglacial channels do not reopen 4. pressure melting seperates the ice from its bed causing it to flow more readily 5. water increases the pressure which adds to the rapid movement 6. the surge occurs and then the glacier resumes to normal flow